The processing capability of communication apparatus is increasing from year to year and, in keeping up therewith, the transmission speed of a backplane is also increasing. The signal speed already exceeded 1 Gbps and is even nearing 10 Gbps. It has been known that a branch (stub) parasitically formed by a through-hole in the backplane is a factor that deteriorates high-speed transmission characteristics. To realize transmission in excess of 10 Gbps or higher, it is mandatory how to avoid the stub in the through-hole from being built up in the backplane.
FIGS. 5A to 5C show a backplane system in a conventional communication apparatus. In this conventional backplane system, a printed circuit board 110, as a backplane, is connected to network cards 130, 150 and a switch card 140 via connectors 120A, 120C and 120B, respectively. Since a press-fit terminal is used in general as a terminal 121 of the connector 120, a through-hole 112 is indispensable in the printed circuit board 110.
In the related art, the following techniques have been proposed in connection with coping with deterioration of characteristics ascribable to through-hole stubs.
[Patent Document 1]
JP Patent Kokai Publication No. JP-P2003-217745A
[Patent Document 2]
JP Patent Kokai Publication No. JP-P2004-165200A
[Patent Document 3]
JP Patent Kokai Publication No. JP-P2004-327690A
[Patent Document 4]
JP Patent Kokai Publication No. JP-P2005-175189A
[Patent Document 5]
JP Patent Kokai Publication No. JP-P2005-35173 LA
[Patent Document 6]
JP Patent Kokai Publication No. JP-P2006-211070A